1. Field of the Invention
The present invention relates to an electric parking brake apparatus capable of activating and deactivating a parking brake of a vehicle by use of electric drive means such as an electric motor.
2. Description of Related Art
Japanese Patent Application Laid-Open (kokai) No. 2001-322537 discloses a conventional electric parking brake apparatus of such a type. The disclosed apparatus includes an electric parking brake control unit, which receives a parking brake activation-deactivation signal generated upon operation of a manual switch and which drives an electric motor on the basis of the signal to thereby activate and deactivate a parking brake.
Further, the electric parking brake control unit is connected to various sensors mounted on the vehicle, and is configured to determine, on the basis of signals from the sensors, whether a condition for starting automatic activation of the parking brake or a condition for starting automatic deactivation of the parking brake is satisfied, and when either of the conditions is satisfied, the electric parking brake control unit automatically activates or deactivates the parking brake in accordance with the satisfied condition. In other words, the conventional apparatus equipped with the above-described electric parking brake control unit is designed to activate or deactivate the parking brake by means of a function of manually controlling the parking brake in response to switch operation (hereinafter referred to as “manual control function”), as well as by means of a function of automatically controlling the parking brake on the basis of signals from various sensors (hereinafter referred to as “automatic control function”).
However, since the electric parking brake control unit of the above-described conventional apparatus includes various input circuits for receiving signals from various sensors and a complicated determination function for determining whether the automatic activation start condition is satisfied, which circuits and function are necessary for accomplishing the above-described automatic control function, the control unit has problems in that the unit is large and of complex configuration.
Some vehicles which carry an electric parking brake apparatus do not require any automatic control function, and in such vehicles, use of the above-described electric parking brake control unit having an automatic control function is not required. In other words, in the case where, among vehicles which carry an electric parking brake apparatus, some vehicles require the automatic control function and the remaining vehicles do not require the automatic control function, there has been a problem in that two types of electric parking brake control units must be prepared; i.e., an electric parking brake control unit having both a manual control function and an automatic control function as described above, and an electric parking brake control unit having only a manual control function and not having an automatic control function.